Nitrogen-doped Mesoporous Carbon Materials Research Articles

Influence of the Nitrogen Precursor in the Development of N-Functionalities in a Mesoporous Carbon Material and Its Effect on the Li–S Cells’ Electrochemistry

Li–S batteries are positioned as a strong alternative for efficient energy storage due to their high theoretical energy density and their theoretical specific capacity (1675 mA h g−1) compared to current Li-ion batteries; however, their commercialization is affected by the rapid decay of the specific capacity as a consequence of the different species of lithium polysulfides that are generated during the charge–discharge processes. The use of nitrogen-doped mesoporous carbon materials has been shown to have the ability to confer electronic conductivity to sulfur and retain the lithium polysulfide species. However, there are not enough studies to help understand how the type of nitrogen precursor influences the development of specific nitrogen functionalities to favor the retention of lithium polysulfide species. This work seeks to determine the effect of the use of different nitrogen precursors on the structural changes of the mesoporous carbon materials prepared, and thus evaluate the electrochemical behavior of Li–S cells correlating the type of nitrogen functionality generated when the precursor is variated with the charge/discharge capacity developed during the cell operation. For this study, different carbon materials were prepared by the variation of the nitrogen source (melamine, ethylenediamine, and hexadecylamine) to obtain a N-doped mesoporous carbon with different distributions of nitrogen functionalities in its structure. The use of the primary amine ethylenediamine as a nitrogen precursor in the formation of structured carbon materials favored elemental sulfur infiltration into its pores, resulting in the maximum sulfur content within the pores and interacting with the carbonaceous matrix (78.8 wt.%). The carbon material prepared with this precursor resulted in a higher content of N-pyridinic functionality, which, combined with the high content of N-pyrrolic, resulted in the highest specific discharge capacity at 0.1 C after 100 cycles when compared to cells assembled with materials derived from the use of melamine and hexadecylamine precursors. The cell assembled with the electrode formed from ethylenediamine as a nitrogen precursor presented an initial discharge capacity of 918 mA h g−1 with a Coulombic efficiency of ~83.4% at 0.1 C after 100 cycles.

High-density atomically dispersed CoNx catalysts supported on nitrogen-doped mesoporous carbon materials for efficient hydrogenation of nitro compounds

Carbon supported atomically dispersed transition metal–nitrogen (MNx) catalysts are promising for catalysis. Synthesis of such catalysts with high densities of MNx sites is an important task. In this work, a facile and scalable method by combining freeze drying and hard templating is presented for the synthesis of N-doped mesoporous carbon supported high-density and exclusive CoNx sites (denoted as CoNx-NMCs). The influences of the drying method (freeze drying and regular drying) on the aggregation of the silica pore forming agent, the precursor and metal species and the properties and performances of the resulted catalysts are investigated. The strong Co2+/histidine and silica/histidine interactions and the homogeneous distribution of the SiO2 nanoparticles for precursor physical isolation are essential to inhibit metal aggregation, sustain N dopant and generate high densities of CoNx sites. The CoNx-OMCs possess high surface areas (440–630 m2/g), uniform mesopores (~ 7 nm), high N contents (2.54–17.84 wt%) and abundant CoNx sites with high single cobalt atom loadings up to 1.7 wt%. The representative catalyst delivers outstanding catalytic performances for hydrogenation of a series of nitro compounds into amines with excellent conversions and selectivities and a high stability with H2 as the reducing agent and water as the solvent. A series of control experimental results clearly reveal the critical role of the CoNx sites for the chemoselective hydrogenation and clarify the influences of the properties of the catalysts on their performances. The work may provide a general approach and some insight for the development of atomically dispersed MNx catalysts with a high metal atom utilization efficiency for the purpose of various catalytic applications.

Highly Active Nitrogen-Doped Mesoporous Carbon Materials for Supercapacitors

Highly Active Nitrogen-Doped Mesoporous Carbon Materials for Supercapacitors

Ultrafine PdCo bimetallic nanoclusters confined in N-doped porous carbon for the efficient semi-hydrogenation of alkynes.

Semi-hydrogenation of alkynes to prepare alkenes is an important reaction in the petrochemical and fine chemical industries. The use of conventional Pd nanoparticle-based catalysts is limited by alkyne over-hydrogenation and low Pd utilization. In this study, a nitrogen-doped mesoporous carbon material (m-NC), which was rich in defect sites after Zn volatilization, was fabricated by the carbonization of ZIF-8. Ultrafine PdCo bimetallic nanoclusters with Co atom-modified Pd active site electronic and compositional structure were highly dispersed and confined in m-NC. As-obtained Pd0.43Co1/m-NC was used for the semi-hydrogenation of alkynes and it exhibited high selectivity with high conversion under mild reaction conditions. Pd0.43Co1/m-NC also exhibited excellent stability in leaching tests and maintained its catalytic activity for at least nine reaction cycles. The highly dispersed active sites in Pd0.43Co1/m-NC served as the active sites for the catalytic semi-hydrogenation of alkynes; as a regulator, the second metal Co effectively improved selectivity, and m-NC endowed the catalyst with excellent stability. The research work presented here may provide a foundation for the design of highly active, selective, and stable Pd-based bimetallic catalysts for selective hydrogenation.

Nitrogen-doped mesoporous carbon material (NCMK-3) as a catalyst for the removal of 4-chlorophenol during persulfate oxidation and its efficiency after reuse

ABSTRACT Persulfate (PS) oxidation of 4-chlorophenol (4CP) is mostly catalysed by relatively expensive metal substrates. In this study, we investigated the influence of nitrogen-doped and non-doped mesoporous carbon materials (NCMK-3 and CMK-3) during persulfate (PS) oxidation of 4CP in water. Batch experiments were conducted such that PS was added to simulated contaminant mixture after 1 h agitation with NCMK-3 and CMK-3. Further, the experiment was carried out at different temperatures, pH ranges, concentrations of persulfate (PS), and different doses of NCMK-3, since it recorded better removal rates compared to CMK-3. The results revealed that NCMK-3 and CMK-3 aided the removal of 4CP from water during persulfate oxidation. When persulfate was added after an hour of equilibration with CMK-3 and NCMK-3, 83% and 92% of 4CP were removed within 20 min, respectively, whereas lower removal rates (≤40) were recorded in the absence of persulfate (PS). The removal rates of 4CP increased with an increase in temperature but reduced in the alkaline medium in the NCMK-3/PS system. The efficiency of the NCMK-3 reduced significantly after it was reused three times. Based on the results, NCMK-3 influences the activity of PS oxidation of 4-chlorophenol (4CP) and exhibited a synergistic effect in the removal of the organic contaminant from water.

Pig manure-derived nitrogen-doped mesoporous carbon for adsorption and catalytic oxidation of tetracycline

Ordered nitrogen-doped mesoporous carbon (NMC) was successfully synthesized with pig manure as the precursor. The resulting NMC materials exhibited excellent capacity of adsorption and potassium persulfate (PS) activation when used as catalysts for the oxidative degradation of tetracycline antibiotics (tetracycline hydrochloride (TH) as the target). For an initial TH concentration of 35 mg/L, the maximum adsorption capacity of NMC material prepared at 700 °C (NMC700) was 122.0 mg/g, and the degradation efficiency in the PS reaction system was 94.8% within 120 min. Investigation of the mechanism indicated that the NMC700 material with specific surface area (SSA) of 275.5 m2/g and 0.7% graphitic N content, provided a large amount of active sites for adsorption and catalytic oxidation of TH. Based on the results of selective degradation and electron paramagnetic resonance (EPR) experiments, a non-radical pathway for the degradation of pollutants was proposed. Chronoamperometry evaluation also supported the conclusion that the NMC material enhanced electron transfer to activate persulfate, accelerating the removal of TH.

Tofu-derived nitrogen-doped mesoporous carbon materials as metal-free catalyst for oxygen reduction reaction

Nitrogen dope mesoporous carbon materials are widely used in the designing of oxygen reduction reaction (ORR) catalysts. How to prepare nitrogen-doped carbons (NC) with broad mass transfer path and preserve abundant ORR active nitrogen functionalities is still a great challenge. Here, nitrogen-doped mesoporous carbon materials are obtained through simply pyrolysis a mixture of renewable biomass (tofu) and ZnCl2. Owing to the effective chemical activation effect during carbonization, the optimal NC could present high porosity (high surface area of 1062 m2 g−1, large pore volume of 0.97 cm3 g−1) and high nitrogen content (7.74 wt%). Benefit from the rich of nitrogen functionalities to create abundant active sites and the well-developed mesoporous structure (high mesopore area 825 m2 g−1 and dual mesopore system with mesopore in both 3 nm and 30 nm) to guarantee fast mass transport and electron transfer, the obtained NC could serve as fine metal-free ORR catalyst, accelerating oxygen reduction reaction via high efficient 4e− oxygen reduction pathway. And more important, NC showed higher stability than commercial Pt/C (20 wt%), which highlight its great potential in the designing of electrocatalyst.

Co-entrapped, N-doped mesoporous carbons prepared from melamine formaldehyde resins with CoCl2 as template for hydrogen evolution

Cobalt-entrapped, nitrogen-doped mesoporous carbon materials have been prepared using melamine formaldehyde resin (MF resin) as precursor and CoCl2 as template. A fraction of CoCl2 can be reduced to Co nanoparticles and wrapped by the nitrogen doped carbon. Meanwhile, the ratio of MF resin to CoCl2 is an important parameter determining the mesoporous structures of the final products. The surface area of the obtained material decreases with the increase in the ratio of MF resin to CoCl2. Electrocatalytic tests show that the obtained catalysts are highly active for hydrogen evolution reaction in both acidic and basic media, achieving a current density of 10 mA cm−2 at 171 and 186 mV under acidic and alkaline conditions, respectively. Additionally, these catalysts also show good long-term stabilities.

Nitrogen-Doped Mesoporous Carbon Material (N-GMC) as a Highly Efficient Catalyst for Carbon Dioxide Fixation Reaction with Epoxides under metal-free condition

A soft template (Brij-35) controlled nitrogen-doped mesoporous carbon material (N-GMC) was prepared from glucose as a carbon source and melamine as a nitrogen source. The synthesized material was characterized by XRD, SEM, HRTEM, XPS, and Raman spectroscopy and nitrogen adsorption and desorption isotherms. Nitrogen enriches carbon material with high surface area and porous channel showed high CO2 fixation reaction at low temperature and ambient pressure. Excellent catalytic activity and reusability showed towards cyclic carbonate synthesis from various epoxides under metal free condition.

Adsorption behaviors of methyl orange dye on nitrogen-doped mesoporous carbon materials

A series of nitrogen-doped mesoporous carbon materials (NMC) with different nitrogen contents (from 9.1 to 11.3wt.%) were prepared using urea and ammonia as economical nitrogen resources by sol–gel method. The NMC materials possessed high surface areas (from 659m2/g to 912m2/g) as well as large number of oxygen-containing and nitrogen-containing groups. The adsorption behaviors of NMC materials for anionic dye methyl orange (MO) were investigated, which are fit excellent for the Langmuir isothermal adsorption equation. All the materials exhibited high adsorption capacity for MO at room temperature. Their adsorption capacity can be adjusted by changing the nitrogen contents in NMC materials. Moreover, treating the NMC material at higher temperature can significantly improve the adsorption capacity for MO. According to the results of characterization, the main features of NMC materials, like large pore size and abundant basic nitrogen-containing groups on the surface, should be related to the excellent adsorption property for MO.

Adsorption of CO2 and H2 on nitrogen-doped porous carbon from ionic liquid precursor

Nitrogen-doped mesoporous carbon material was prepared via a simple one-step thermolysis method via the carbonization of ionic liquid, 1-cyanomethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([MCNIm]+[Nf2T]−). The nanostructure of the resultant carbon material was characterized by X-ray diffraction(XRD) and transmission electron microscopy(TEM) and the types of N-containing groups of the carbon material were investigated by X-ray photoelectron spectroscopy(XPS). The N-content of the carbon material is 18.6%(mass fraction) based on the elemental analysis. The produced mesoporous carbon material was further used as the solid sorbent for H2 and CO2. The hydrogen uptake capacity and H2 isosteric heat of the carbon material were discussed. Furthermore, the nitrogen-containing carbon material as good sorbent shows relatively high adsorption and separation ability for CO2 from CH4, for which the heat of CO2 adsorption(Q st) is 31.8 kJ/mol. The mesoporous structure and nitrogen functionality make the carbon material with high adsorption capacity and selectivity for CO2 and ability to store H2, indicating that this kind of nitrogen-doped carbon material originated from ionic liquids is a promising sorbent material for high-performance separation and adsorption.

The large electrochemical capacitance of nitrogen-doped mesoporous carbon derived from egg white by using a ZnO template

We used ZnO nanoparticles as a hard template and egg white as a precursor to successfully synthesize nitrogen-doped mesoporous carbon materials and the as-prepared material was further used as an electrode material for supercapacitor applications.

Nitrogen-doped mesoporous carbon as low-cost counter electrode for high-efficiency dye-sensitized solar cells

Abstract We demonstrate an excellent performance of nitrogen-doped mesoporous carbon (NMC) as a low-cost counter electrode for dye-sensitized solar cells. NMC materials are prepared using melamine-formaldehyde resin as carbon precursor and silica nanoparticles as template. Nitrogen adsorption analysis shows that the as-prepared NMC samples had a high surface area, large pore volume and bimodal mesopore structure with maxima at ∼3.5 nm and ∼16 nm. Electrochemical impedance spectroscopy tests reveal a low charge-transfer resistance of 1.45 Ω cm 2 for NMC electrode in iodide/triiodide redox electrolyte. Such excellent electrocatalytic activity for iodide/triiodide redox reaction of NMC electrode can be attributed to a unique combination of nitrogen doping, bimodal mesopore structure and high surface area. A power conversion efficiency of 7.02% is achieved for the dye-sensitized solar cell with NMC counter electrode, which is comparable to that of the device with Pt counter electrode. These results reveal that NMC electrode is a promising low-cost alternative to Pt counter electrode in dye-sensitized solar cells.

Nitrogen-doped mesoporous carbons originated from ionic liquids as electrode materials for supercapacitors

Nitrogen-doped mesoporous carbon materials are prepared via carbonization of a room temperature ionic liquid, 1-butyl-3-methylimidazolium dicyanamide (BMIMdca), using a mesoporous silica template (SBA-15). The nitrogen content and nanostructure of the resultant carbon materials are highly dependent on the carbonization temperature. The produced porous carbon materials were further applied as the electrode materials for supercapacitors. The porous structure and nitrogen functionalities enable carbon materials with a specific capacitance of 210 F g−1 at a current density of 1 A g−1 in a 6 M KOH aqueous solution. Furthermore, the nitrogen-doped porous carbon materials maintain a high capacitance retention capability (∼95%) after 1000 cycles at a current density of 1 A g−1, indicating that this kind of nitrogen-doped carbon material originated from room temperature ionic liquids is a promising electrode material for high-performance supercapacitors. These results may provide a facile synthesis of sulfur and nitrogen or multi-element doped porous carbon materials originated from ionic liquids for supercapacitors.

Synthesis and Properties of Nitrogen-Doped Mesoporous Carbon Materials Obtained by Templating of SBA-15 with Melamine-Formaldehyde Resin

Nitrogen-doped mesoporous carbon materials have been synthesized by using melamine-formaldehyde resin as carbon precursor and SBA-15 as a removable template. The structure of the materials was investigated by X-ray diffraction, BET specific surface area analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. X-ray and BET studies confirmed that a pore nanostructure is inherited from the silica templates. Fourier transform infrared spectroscopy analysis showed N atoms are strongly bonded in the carbon structure in heterocycles or nitrile functions. These mesoporous nitrogen-doped carbon materials exhibits textural properties with BET surface areas ranging between 400 and 600 m2/g and uniform pore size(3.9 nm). The mechanism of carbonization process is studied by thermogravimetric analysis. The ratio of melamine/formaldehyde plays an important role during the carbonization process for the surface areas and textural properties, and element analysis reveals that the nitrogen content of the mesoporous carbon materials is as high as 10wt%.

A rapid hard template method for the synthesis of N-doped mesoporous carbon replicated from TUD-1

A porous silica material, TUD-1, was used as the hard template to synthesize nitrogen-doped mesoporous carbon (NMC) using a modified hard template method with fewer synthesis steps, compared to the conventional method. This method starts with the formation of a triethanolamine (TEA)/TUD-1 composite, followed by direct carbonization in CH4, where TEA and CH4 are used as nitrogen (N) and carbon precursors, respectively. The direct use of the templating agent TEA as the N precursor skips the calcination step and the infiltration of another N precursor, simplifying the conventional hard template method. The obtained NMC material possesses a similar three dimensional sponge-like mesostructure to its parental TUD-1. Several characterization techniques were used to characterize textural structure, carbon yield, N content, graphitization and surface chemical composition of the resulting NMC materials. These properties can be controlled by manipulating synthesis parameters, such as carbonization temperatures, CH4 flow rate, CH4 partial pressure, heating ramp rate and the structural characteristic of the TUD-1 template. In addition, NMC with high N content (9.6at.%) was also synthesized using acetonitrile as an alternative N-containing precursor.